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A CONCEPT FOR CHERENKOV TELESCOPES FOR ULTRA-II

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A CONCEPT FOR CHERENKOV TELESCOPES FOR ULTRA-II Florian Goebel, Anton Kabelschacht, Eckart Lorenz – PowerPoint PPT presentation

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Title: A CONCEPT FOR CHERENKOV TELESCOPES FOR ULTRA-II


1
A CONCEPT FOR CHERENKOV TELESCOPES FOR ULTRA-II
Florian Goebel, Anton Kabelschacht, Eckart
Lorenz
2
  • SUMMARY PHYSICS GOALS AND PROSPECTS
  • Study of the spectra of
    galactic point sources as well as extended
    galactic sources up to around 100 TeV
  • Details of spectral cut-off parameters of these
    sources
  • Spectral shapes of low redshift AGNs with high
    sensitivity
  • All-sky monitoring with high sensitivity, alerts
    for the low threshold array and quick switchover
    to dedicated
  • sources in case of flaring sources
  • Study of diffuse gamma-radiation from the
    galactic plane
  • Study of possible isotropic
    gamma-emission from Topological Defects



  • Study of the chemical
    composition between 1012-1015
  • Search for fine structures in
    the general CR spectrum
  • Long-term studies of some
    flaring sources
  • Possibly a search for
    quark-gluon plasma (needs theoretic input)
  • Extension of GLAST studies
  • No studies of GRBs
  • May be use of the array as an
    air fluorescent detector in the 1016-1018 eV
    range. Needs some bright ideas
  • for the trigger,
    attractive for small groups
  • Coincidence studies with large
    VHE neutrino detectors for some dedicated source
    candidates.
  • Crazy idea study of high
    atmosphere small discharges (Elfs etc) see EUSO
    proposal.

3
  • BASIC DESIGN CONSIDERATIONS
  • IT IS IMPOSSIBLE TO BUILD AN OPTIMAL DETECTOR
    THAT SPANS 4 ORDERS OF
  • MAGNITUDE IN ENERGY DUE TO THE STEEP POWER LAW
    OF FLUXES
  • ONE NEEDS TWO DETECTOR CONFIGURATIONS FOR THE CTA
    TO SPAN FROM
  • 10 GEV TO 100 TEV
  • LEA ( 10GEV - gt 1 TEV)
    ULTRA II lt (1 TEV - gt100 TEV)
  • ULTA II (ULTRA LARGE TELESCOPE ARRAY) 100
    TELESCOPES SPREAD OVER 1-2 km2
  • EACH TELESCOPE WITH 18 m2 MIRROR AREA
  • SENSITIVITY 10 x HIGHER THAN PAST ARRAYS
  • LOWER THRESHOLD LIMIT 400 GEV IN ZENITH
    POSITION BUT HIGH g/h SEPARATION
  • POWER AT 1 TEV
  • UPPER OPERATION LIMIT 200 TEV

4
  • SOME SPECIAL ISSUES
  • THE TECHNICAL CONSIDERATIONS ARE NOT VERY
    CHALLENGING COMPARED
  • TO THE LEA PART
  • THE DOMINANT COST IS DRIVEN BY THE CAMERA -gt USE
    OF CLASSICAL PMTS
  • -gt USE OF 25 mm HEMISPHERICAL PMTS
    (CONSERVATIVE, LOW RISK, PLENTY
  • OF EXPERIENCE, NO NEED TO MAXIMIZE QE, PANEQUE
    LACQUER OK,
  • PMTS MATURE, G-APDS STILL IN EARLY DEVELOPMENT
    PHASE)
  • INSTEAD OF INVESTING IN IMPROVING QE BY FANCY
    WORK-
  • -gt INCREASE MIRROR AREA-gt 18m2 (gt 2x HEGRA IACT
    AREA)
  • NEARLY ENTIRELY TO BE CONSTRUCTED BY INDUSTRY
  • ALL WORK CAPACITY NEEDED FOR HESS II, MAGIC II
    AND LEA
  • AIM FOR CONSTRUCTION TIME 4 YEARS
  • INSTALL A TELESCOPE BY 4-5 PEOPLE IN lt 1 WEEK

5
  • SOME TECHNICAL ISSUES
  • FOUNDATION a la HEGRA SIMPLE CONCRETE BLOCK 3
    x3x1 m3 thin working platform
  • UNDERCARRIAGE LIKE FOR HEGRA CTS WITH CRANE BALL
    BARING
  • PLUS ROTATING WORKING PLATFORM
  • UPPER STRUCTURE LIKE MAGIC SPACE FRAME- ALUMINIUM
    TUBES
  • BUT ONLY 2 LAYER SPACE FRAME USING A TETRAEDER
    AS BASIC ELEMENT
  • DRIVE MOTORS STEPPING MOTORS LIKE FOR HEGRA
  • CAMERA SUPPORT MAST GOTHIC ARC (PREFORMED
    I-BEAM) HOLD BY
  • PRESTRESSED STEEL CABLES
  • MIRRORS HEXAGONAL, MADE FROM HIGHGLY REFLECTIVE
    AL-ANOD PLATES
  • SUPPORTED BY HEXCELL SANDWICH (a la CURRENT
    PADOVA CONSTRUCTION)
  • NO NEED FOR DIAMOND MACHINING
  • HIGH WEATHER RESISTANCE DUE TO MULTILAYER
    COATING
  • POORER FOCUSSING THAN IN MAGIC BUT OK BECAUSE
    OF 0.25 PIXELS
  • ALTERNATIVE MIRROR PRODUCTION REPLICA METHOD -
    WUERZBURG
  • ALTERNATIVE MIRROR PRODUCTION THIN ALUMINIZED
    GLASS FOILS BACKED BY
  • HEXCELL SANDWICH
  • NO ACTIVE MIRROR CONTROL BUT AUTOMATIC MIRROR
    ADJUSTMENT EVERY

6
  • SOME TECHNICAL ISSUES, II
  • CAMERA 5 Ø, 0.25 PIXEL SIZE -gt ALMOST MAGIC
    LAYOUT INNER SECTION
  • FOR f 7 m
  • -gt COPY OF MAGIC I PRINTED CIRCUIT
  • PMTS 6 STAGE PMTS (GAIN 105) TRANSIMPEDANCE
    PREAMP
  • BANDWITH CAN BE LOWER THAN FOR MAGIC PMTs
  • DYNAMIC RANGE OF PREAMP 500 SUFFICIENT
  • ET SAYS THAT PRICE FOR 33000 PMTS CAN BE
    100/PMT IF NO UV GLAS NEEDED
  • ET CAN BUILD CAMERA PRINT CIRCUIT, TEST AND
    ASSEMBLE, HT PREAMPS
  • SHORT COAX CABLES (RG174) FROM CAMERA TO READOUT
    ELECTRONICS
  • LOCATED IN SPACE FRAME
  • CAMERA WINDOW UV TRANSMITTING PLEXIGLASS
  • LIGHT CATCHERS a la MAGIC, LINED WITH POSSIBLY
    DIELECTRIC MIRROR FOIL
  • HT IN CAMERA, NEW COMPACT VERSION
  • DIGITIZER SWITCHED CAPACITOR ARRAY (DOMINO CHIP)
    ACTING BOTH AS
  • DELAY AND F-ADC (500 MHZ, HIGHER FREQ. NOT
    NEEDED). MAIN PROBLEM
  • CURRENT READOUT MUCH TOO EXPENSIVE -gt CUSTOM IC
  • TRIGGER RATHER SIMPLE 2 FOLD NEXT NEIGHBOR FOR
    EACH TELESCOPE

7
  • SUMMARY TELESCOPE PARAMETERS
  • 1. mirror area 18 m2
  • 2. Mirror layout see Fig 1
  • 3. Focal distance 7 m (f/D 1.4)
  • 4. Number of mirror elements 18
  • 5. Mirror profile quasispherical, Davis-Cotton
  • 6. Operation range Azimuth 350, Declination
    100-gt -75
  • 7. Camera diameter 5
  • 8. Pixel size 0.25
  • 9. Nr of pixels 330
  • 10. Photon sensors PMTs, 1 Ø, hemispherical, 6
    dynodes, max gain 105
  • 11. Max slewing speed 60/min (fast slewing not
    needed)
  • 12. Drive motors stepping motors with planetary
    gears of small backlash
  • Angular measurements by 13 or 14 bits absolute
    shaft encoders read out by CAN bus
  • or equivalent bus
  • Trigger each telescope two next neighbour
    pixels. Between telescopes wide gate coincidence
  • triggering coinciding telescopes. Under normal
    conditions at least 2 telescopes should trigger
    in
  • coincidence. Alternatively, for all sky monitor
    observations, telescopes trigger autonomously.
  • For air fluorescence studies a special trigger
    is needed

8
SUMMARY TELESCOPE PARAMETERS COST
ESTIMATE 1. Cost per telescope Total cost lt 200
k ? Concrete foundation 5 k ? Mechanical
structure 25 k ? Motors, encoders, power 10
k ? Mirrors 10-20 k ? Camera DAQ 110
k ? Auxiliary equipment 35 k TOTAL COST OF
ULTRA II 25 M 5M DEVELOPMENT COSTS 100
TELESCOPES If you need finer pixels either more
money or fewer telescopes. For 0.12pixels
either 3x fewer telescopes or price 75 M
9
  • A POSSIBLE DEVELOPMENT ROAD
  • A) MONTE CARLO STUDIES
  • CROSS CHECK CORRECTNES OF HADRONIC SHOWER
    PHYSICS
  • SIMULATION OF SENSITIVITY, TRIGGER PERFORMANCE
  • B)LIST OF TECHNICAL DEVELOPMENTS
  • HIGH PRIORITY DEVELOPMENTS
  • PROTOTYPE MIRROR DEVELOPMENTS
  • SPECIAL ASIC FOR DOMINO READOUT
  • TWOFOLD NEXT NEIGHBOR COINCIDENCE LOGIC
  • LOW POWER DISCRIMINATOR ASIC WITH EASY EXTERNAL
    CONTROL OF THREHOLD
  • AND DELAY
  • MEDIUM PRIORITY
  • LOW POWER HT UNITS FOR PMTS
  • MECHANICAL DESIGN OF TELESCOPE STRUCTURE
  • ACTIVE MIRROR ADJUSTMENT

10
Not useful, cutoff in UV
11
Multilayer Quartz-TiO2
Price of MIRO 4300 per panel of 1250x1250 mm,
0.5 mm 20 panels for developments. 80 /panel
resp. mirror 2000 panels 25 /panel resp.
mirror Note 300G is not weather resistant
12
Mirror work at Wuerzburg
13
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14
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15
POSSIBLE MIRROR LAYOUT

16
LAYOUT MIRRORS (BLUE) AND TOP LAYER OF SPACE
FRAME (BLACK) LOCATION OF ACTUATORS/FIX POINTS OF
MIRROR PANELS
ACTUATORS
17
LAYOUT MIRROR AND TOP LAYER SUPPORT FRAME
CAMERA SUPPORT MAST
MIRROR
108 cm
CAMERA SUPPORT MAST
540 cm
18
BASIC SPACE FRAME ELEMENT MAGIC
BASIC ELEMENT FOR ULTRA

CONSIDERABLY STIFFER
19
PART OF TRIGGER LOGIC

2 PIXELS FIRING 2 PIXELS FIRING
ACQUIRE
ACQUIRE
20
POSSIBLE MODES OF OPERATION
HIGHEST SENSITIVITY FOR SINGLE SOURCE
SEARCH/STUDY COMBINE LEAULTRA II AND
FOCUS ONTO ONE SOURCE ALL SKY MONITORING
POINT ALL TELESCOPES TO DIFFERENT POINTS ON SKY
COVER 0.5 STERAD BUT WITH LOW
SENSITIVITY CAN ALSO BE USED AS A FLYS EYE TYPE
DETECTOR VARIANT COMBINE 3(2) TELESCOPES FOR
STEREO SUBCELLS AND POINT TO DIFFERENT POINTS ON
THE SKY COVERS 0.15 STERAD, BUT WITH HIGHER
SENSITIVITY (2-3) SPLIT ARRAY INTO TWO(2,3..)
PARTS AND USE ONE PART FOR HIGH SENSITIVE SOURCE
STUDIES WHILE USING OTHER (SMALLER) PART FOR
LONG-TERM MONITORING OF DEDICATED FLARING
SOURCES (AGNS) FOR VARIOUS STUDIES .MONITORING
TOGETHER WITH LARGE NEUTRINO DETECTORS
21
CONCLUSIONS
A 100 TELESCOPE ARRAY CAN BE BUILD WITHIN 4
YEARS (ASSUMES LARGE INDUSTRIAL SERIES
PRODUCTION) MOST DEVELOPMENT CAPACITY NEEDED FOR
LEA PART A COST OF 25 M IS NOT UNREALISTIC THE
BALANCE BETWEEN THE WISH FOR BETTER PERFORMANCE
AND LIMITED BUDGET WILL BE BETWEEN THE NR OF
TELESCOPES AND CAMERA PERFORMANCE RELATIVE
CONSERVATIVE APPROACH POSSIBLE, NO CHALLENGING
NEW AND UNPROVEN COMPONENTS NEEDED READOUT
ELECTRONICS TRIGGER VARIANTS MOST DEMANDING MC
SIMULATIONS NOT MADE MC SIMULATIONS WILL MOST
LIKELY GIVE GUIDANCE FOR SOME CRITICAL
PARAMETERS SUCH AS TELESCOPE SPACING, PIXEL SIZE
AND CAMERA FOV
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